Sputter-deposited CdMgTe for rear contact to CdSeTe/CdTe solar cells

CdTe-based photovoltaic device performance improvement is predominantly limited by open-circuit voltage. This work approaches the voltage deficit challenge through the incorporation of a cadmium magnesium telluride (CdMgTe) electron reflector layer at the back of 1.5-mu m CdSeTe/CdTe absorbers to reduce back-surface recombination through a conduction band offset. A sputtered CdMgTe electron reflector layer permitted low fabrication temperatures and circumvented the intolerance of CdMgTe to thermal processing present in traditional close-space sublimation (CSS)-deposited CdMgTe devices. We demonstrate that sputtered CdMgTe simultaneously promotes the retention of chlorine passivation and magnesium which is not feasible with CSS fabrication. We also show the importance of the Cu and Te back contact order in CdMgTe devices. Through the optimization of the sputtered CdMgTe substrate temperature, doping, and back structure configuration, 1.5 mu m CdSeTe/CdTe devices with a sputtered CdMgTe layer achieved an efficiency of 16.0%, significantly higher than with CSS CdMgTe, and demonstrated partial enactment of electron-reflector behavior.

Automated summary

CdTe-based photovoltaic devices have limited performance improvement due to open-circuit voltage. This study addresses this issue by incorporating a CdMgTe electron reflector layer to reduce back-surface recombination. The sputtered CdMgTe layer enables low fabrication temperatures and retains important elements such as chlorine passivation and magnesium. By optimizing the back contact order and parameters of the CdMgTe layer, CdSeTe/CdTe devices achieve a higher efficiency of 16.0% compared to traditional CSS CdMgTe.